Stone Industrial Corporation of College Park, Maryland, has had a long-term development project related to a copper-plated combustion chamber concept for reciprocating internal combustion engines. A majority of their experience with this concept has been with Diesel engines. Their work has shown reduction in Diesel smoke levels and some improvement in fuel economy. As an extension of this effort and to investigate the effect of their copper-plated combustion chamber concept in a light duty automotive application, Stone prepared two gasoline-powered vehicles. The Emission Control technology Division was contacted by Stone in regard to conducting confirmatory testing on these vehicles. Emissions data from these vehicles presented by Stone demonstrated the potential of achieving low levels of all three emissions. Thus, test work was undertaken by the Test and Evaluation Branch.